Sulfuric acid at high levels of concentrations over 75% and especially 90 to 99% is particularly corrosive to metal vessels and apparatus handling it. For the most part, higher cost nickel-base alloys have been used in the manufacture of such articles, limited to the form of castings. U.S. Pat. No. 3,311,470 discusses the problem in great detail. The specification clearly presents the problems in the commercial handling of high concentrations of sulfuric acid.
U.S. Pat. No. 3,615,368 discloses the effects of nitrogen in a corrosion-resistant steel containing chromium, nickel and silicon. The steel may also contain molybdenum and manganese. U.S. Pat. No. 4,487,630 discloses a wear-resistant steel containing chromium, nickel, silicon, carbon and cobalt plus optional contents of manganese, molybdenum, tungsten, vanadium, zirconium, tantalum, columbium, boron, titanium and hafnium. U.S. Pat. Nos. 4,033,767 and 3,758,269 relate to nickel-chromium alloys that are rich in silicon and corrosion resistant. All of the patents described above, as a group, disclose alloys that have wear-resistant characteristics and corrosion-resistant characteristics; however, none has a good combination and balance of both characteristics together with a high degree of ductility and low cost.
There is a great need in the chemical industry for a low cost alloy that (1) may be produced in the form of wrought products; (2) is resistant to sulfuric and other acids; (3) has good strength and ductility and (4) is readily weldable. Furthermore, the alloy must have a high degree of galling-wear and stress corrosion cracking resistance for use in industrial applications. In actual practice, the present art has no ideal solution to the problem. The high cost nickel-base alloys generally are difficult to produce, shape and weld in chemical processing applications. The wroughtable nickel-base alloys do not have adequate wear resistance.